The present invention relates to the field of absorbable sutures. More particularly, the present invention relates to a coated suture having improved tie-down properties.
Suture materials are generally classified as absorbable or non-absorbable, with each type of suture being preferred for different applications. Absorbable suture materials are preferred for applications in which the sewn tissues after healing will hold together without suture reinforcement and in which a non-absorbed suture material may provide the possibility of an adverse body reaction over an extended period of time. Suture materials are considered to be absorbable if they disappear from the sewn tissue within a year after surgery, but most absorbable suture materials disappear within shorter periods of time.
The most commonly employed absorbable suture materials are catgut and extruded collagenous materials. More recently sutures have been developed from synthetic polymers which are absorbable, strong, uniform and dimensionally stable, storable in the dry state and sterilizable.
A significant problem associated with the early synthetic absorbable sutures was difficulty in knot placement. The braid was rough, preventing the surgeon from sliding the knots down the suture and locating those knots accurately for good tissue approximation. To solve this problem, various coating materials have been applied to absorbable sutures. A number of United States patents disclose the use of different coating materials.
U.S. Pat. No. 4,027,676 issued June 7, 1977 discloses an absorbable suture coated with a multicomponent composition comprising (a) an absorbable film-former, (b) an absorbable lubricant, and (c) an absorbable hydrophobic material. This coating has the effect of stiffening the suture so it becomes wire-like rather than soft, smooth and flexible.
U.S. Pat. No. 4,047,533 issued Sept. 13, 1977 discloses an absorbable suture coated with a block copolymer of polyoxyethylene and polyoxypropylene. This coating provides good knot slip-down but knot security is lost and the surgeon must tie four or five knots instead of three to maintain a stitch securely.
U.S. Pat. No. 3,896,814 issued July 29, 1975 discloses the use of a low molecular weight (400) poly(alkylene oxide) as a hygroscopic agent to improve the suppleness of collagen sutures. In the above patent, the low molecular weight poly(alkylene oxide) is used as a humectant for retaining water in the collagen fiber.
Thus, there is a continuing need for a coating for an absorbable suture resulting in a suture having simultaneous improvement in knot security, knot slip-down and hand.